A semiconductor laser

Abstract

The application provides a semiconductor laser, comprising a substrate, an epitaxial structure and a first barrier layer, wherein the epitaxial structure comprises a first confinement layer, a first waveguide layer, an active region, a second waveguide layer and a second confinement layer arranged in a stack from bottom to top. The second confinement layer and part of the second waveguide layer are arranged as a protrusion extending vertically in a direction away from the substrate to form a ridge-shaped part, and a step region is formed on the second waveguide layer on both sides of the ridge-shaped part. By arranging the bottom end of the ridge-shaped part on the second waveguide layer, the injection area of carriers into the active region is reduced when the semiconductor laser is forward conducting, and the injection efficiency of the carriers is improved. Meanwhile, by arranging the second barrier layer on the step region and the sidewall of the ridge-shaped part, the leakage caused by the diffusion of part of the carriers to both sides of the ridge-shaped part or the injection of the active region from both sides of the ridge-shaped part can be effectively prevented, the injection efficiency of the carriers is further improved, and the output power of the semiconductor laser is improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor-related technologies, and in particular to a semiconductor laser. Background Technology

[0002] In recent years, semiconductor lasers have developed rapidly. They have advantages such as compact structure, low cost and easy control of light field, and are widely used in industrial processing, laser display and lighting, optical communication, laser therapy and other fields.

[0003] Compared to strip-gain guided lasers and buried-structure high-refractive-index guided lasers, ridge waveguide semiconductor lasers not only have a simple structure, can be obtained directly through a single epitaxial step, but also provide carrier injection guidance, improving current injection efficiency, thus making them a common laser structure. In existing ridge waveguide semiconductor lasers, the epitaxial structure design and manufacturing process are crucial factors affecting the luminous efficiency and output performance. Current technology typically etches the upper confinement layer of the epitaxial structure into a partially protruding ridge waveguide structure. Utilizing the characteristic that the ridge waveguide structure can reduce the current injection area in the active region when the laser is forward-biased, this improves current injection efficiency and lowers the device's threshold current.

[0004] However, how to provide a new semiconductor laser that can further improve the output power of semiconductor lasers based on existing technologies has become one of the important performance indicators for those skilled in the art to study high-power semiconductor lasers. Summary of the Invention

[0005] The purpose of this application is to provide a semiconductor laser that can reduce the expansion of charge carriers to both sides of the ridge during forward conduction, improve the carrier injection efficiency, and further improve the output power of the semiconductor laser.

[0006] In a first aspect, embodiments of this application provide a semiconductor laser, comprising:

[0007] Substrate;

[0008] An epitaxial structure is formed on the substrate, including a ridge portion and a stepped region;

[0009] A first barrier layer is formed on the extensional structure, the first barrier layer covering the stepped area and extending to cover the sidewall of the ridge portion;

[0010] The epitaxial structure includes a first confinement layer, a first waveguide layer, an active region, a second waveguide layer, and a second confinement layer stacked from bottom to top. The ridge portion is configured as a protrusion extending upward from within the second waveguide layer in a direction away from the substrate, and includes at least the second confinement layer and a portion of the second waveguide layer. The stepped region is formed on the second waveguide layers on both sides of the ridge portion.

[0011] Compared with the prior art, the beneficial effects of this application are at least as follows:

[0012] This application provides a semiconductor laser, including a substrate, an epitaxial structure formed on the substrate, a first barrier layer formed on the epitaxial structure, and the epitaxial structure further including a first confinement layer, a first waveguide layer, an active region, a second waveguide layer, and a second confinement layer stacked from bottom to top. The second confinement layer and a portion of the second waveguide layer are configured as vertically extending protrusions in a direction away from the substrate to form ridges, and stepped regions are formed on the second waveguide layers on both sides of the ridges. By placing the bottom end of the ridge on the second waveguide layer near the active region, the injection area for carriers into the active region is reduced when the semiconductor laser is forward-biased, thereby improving the carrier injection efficiency and increasing the output power of the semiconductor laser.

[0013] Meanwhile, this application provides a semiconductor laser that forms an NPN junction by disposing a second blocking layer on the sidewalls of the stepped region and the ridge portion, and setting the conductivity type of the first blocking layer to be the same as that of the first confinement layer and the first waveguide layer, but different from that of the second waveguide layer and the second confinement layer. This can replace the insulating layer in the prior art, effectively preventing leakage caused by the diffusion of some charge carriers to both sides of the ridge portion, or injecting active regions from both sides of the ridge portion, and further improving the carrier injection efficiency, thereby increasing the output power of the semiconductor laser.

[0014] Furthermore, this application forms a hard mask layer at a predetermined position on the epitaxial structure and uses a dry etching process combined with IPC to obtain a ridge with better sidewall verticality. This improves the top-narrow and bottom-wide morphology of the ridge formed by photolithography in the prior art, avoids the problem of elliptical laser spot caused by the large aspect ratio of the emitted laser in the existing semiconductor laser, and improves the light output effect of the semiconductor laser. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic cross-sectional view of a semiconductor laser according to an embodiment of this application;

[0017] Figure 2 This is a schematic cross-sectional view of a semiconductor laser according to the prior art;

[0018] Figure 3 This is a schematic cross-sectional view of the ridge section of a semiconductor laser according to the prior art;

[0019] Figures 4-6 This is a cross-sectional structural schematic diagram illustrating the ridge formation process of a semiconductor laser according to an embodiment of this application;

[0020] Figures 7-9 A cross-sectional structural schematic diagram of a semiconductor laser according to embodiments of this application is shown.

[0021] Illustration:

[0022] 100 Substrate; 200 Epitaxial structure; 201 Ridge; 202 Step region; 210 First confinement layer; 220 First waveguide layer; 230 Active region; 240 Second waveguide layer; 241 Second lower waveguide layer; 242 Second upper waveguide layer; 250 Second confinement layer; 260 Second barrier layer; 310 First barrier layer; 320 Insulating layer; 410 Hard mask layer; 420 Photoresist; 500 Buffer layer; 610 Ohmic contact layer; 620 First electrode layer; 630 Second electrode layer. Detailed Implementation

[0023] The following specific embodiments illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or operated through other different specific embodiments, and various details in this application can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application.

[0024] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the term "connection" should be interpreted broadly. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. Furthermore, the terms "first" and "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0025] According to one aspect of this application, a semiconductor laser is provided. See also Figure 1 The semiconductor laser includes a substrate 100 on which an epitaxial structure 200 is formed, and a first barrier layer 310 is formed on the epitaxial structure 200. The epitaxial structure 200 includes a ridge portion 201 and a stepped region 202. The ridge portion 201 is disposed at one end away from the substrate 100 and is configured as a ridge protrusion extending upward in a direction away from the substrate 100. The stepped regions 202 are disposed on opposite sides of the ridge portion 201. The first barrier layer 310 is disposed on the stepped regions 202, covering the surface of the stepped regions 202 and extending upward to cover the sidewalls on both sides of the ridge portion 201.

[0026] The epitaxial structure 200 is formed on the substrate 100 and includes a first confinement layer 210, a first waveguide layer 220, an active region 230, a second waveguide layer 240, and a second confinement layer 250 stacked from bottom to top. The second waveguide layer 240 further includes a second upper waveguide layer 242 and a second lower waveguide layer 241, with the second upper waveguide layer 242 disposed on the second lower waveguide layer 241, covering only a portion of the surface of the second lower waveguide layer 241. The ridge portion 201 includes a first end and a second end opposite to each other. The first end is the end of the second confinement layer 250 away from the substrate 100, and the second end is the end of the second upper waveguide layer 242 close to the second lower waveguide layer 241. The ridge portion 201 extends upward from the second waveguide layer 240 and includes at least a second upper waveguide layer 242 and a second confinement layer 250, with the second end separated from the active region 230 only by the second lower waveguide layer, and the step region 202 is formed on the upper surface of the second lower waveguide layer 241 located on both sides of the ridge portion 201.

[0027] Figure 2This is a schematic diagram illustrating the structure of a semiconductor laser according to the prior art. The semiconductor laser also includes a substrate 100 and an epitaxial structure 200, as well as a ridge-shaped portion 201 disposed on the epitaxial structure 200 and protruding from one end away from the substrate 100. The epitaxial structure 200 includes a first confinement layer 210, a first waveguide layer 220, an active region 230, a second waveguide layer 240, and a second confinement layer 250, all stacked together. Figure 2 It can be seen that the ridge portion 201 of the semiconductor laser only includes the second confinement layer 250, and is at least separated from the active region 230 by the first waveguide layer 220 and part of the second confinement layer 250. That is to say, the vertical distance D2 between the bottom end of the ridge portion 201 and the active region 230 in the prior art is much greater than the vertical distance D1 between the second end of the ridge portion 201 and the active region 230 in this application.

[0028] Those skilled in the art will understand that the ridge portion 201 of a semiconductor laser can achieve two-dimensional confinement of light and charge carriers. During the process of current being injected into the active region 230 through the ridge portion 201, it diffuses to both sides of the ridge portion 201 or enters the active region 230 from both sides of the ridge portion 201, expanding the area of ​​the current injection region. This leads to a decrease in the carrier injection efficiency, thereby affecting the output power of the semiconductor laser. In other words, with the same bottom cross-sectional area of ​​the ridge portion 201, after the semiconductor laser is powered on, the larger the distance between the bottom of the ridge portion 201 and the active region 230, the larger the area of ​​the current injection region into the active region 230, resulting in lower carrier injection efficiency and lower laser output power. Correspondingly, by reducing the gap between the bottom end of the ridge portion 201 and the active region 230, the smaller the gap between the bottom end of the ridge portion 201 and the active region 230, the more direct the path for carriers to be injected into the active region 230 becomes. This reduces the area of ​​the current injection region within the active region 230, decreases the diffusion rate of carriers to both sides of the ridge portion 201, improves the carrier injection efficiency, and thus increases the output power of the laser.

[0029] This application extends the second end of the ridge portion 201 into the second waveguide layer 240, so that the ridge portion 201 and the active region 230 are separated only by the second lower waveguide layer 241. That is, based on the prior art, the etching depth in the vertical direction during the formation of the ridge portion 201 is further increased, so that the step region 202 is directly formed on the second lower waveguide layer 241 from the second confinement layer 250 in the prior art. This reduces the spacing between the second end and the active region 230, reduces the injection area of ​​current injected into the active region 230 when the semiconductor device is powered on, improves the carrier injection efficiency when the semiconductor laser is turned on, and further improves the output power of the semiconductor laser.

[0030] Furthermore, by Figure 2 It is understood that in the prior art, the second limiting layer 250 located on both sides of the ridge portion 201 not only forms a stepped region 202, but also includes an insulating layer 320 covering the upper surface of the stepped region 202 and the sidewalls on both sides of the ridge portion 201, in order to reduce the diffusion of charge carriers towards both sides of the ridge portion 201 and thus reduce leakage. For example, the insulating layer 320 typically includes silicon dioxide (SiO2). However, silicon dioxide, as an insulating layer 320, has poor insulation performance. Especially when the laser is forward-biased, some charges will still tunnel through the insulating layer 320 under the influence of the electric field, leading to leakage.

[0031] This application forms a first blocking layer 310 on the sidewalls of the step region 202 and the two sides of the ridge portion 201, and sets the conductivity type of the first blocking layer 310 to be the same as that of the first confinement layer 210 and / or the first waveguide layer 220 as N-type, and different from that of the second confinement layer 250 and / or the second waveguide layer 240. Thus, when the laser is forward-biased, the first blocking layer 310 can form a PN junction with the second confinement layer 250 and the second waveguide layer 240, which can replace the insulating layer 320 to effectively prevent current from being injected into the active region 230 from both sides of the ridge portion 201, and further improve the carrier injection efficiency and the output power of the semiconductor laser.

[0032] Furthermore, see Figure 3 In existing technologies, after the insulating layer 320 is formed, a step of removing the photoresist 420 on the top of the ridge portion 201 is usually included (the photoresist 420 is used to pattern the second confinement layer 250 to form the step region 202 and the ridge portion 201). The removal process of the photoresist 420 can easily cause damage or detachment of the insulating layer 320 formed on the sidewall of the ridge portion 201, resulting in leakage current in the semiconductor laser on both sides of the sidewall of the ridge portion 201. In addition, due to its natural properties, the photoresist 420 has a certain range of slope angle between its edge sidewall and the horizontal plane. As a result, after the ridge portion 201 and the step region 202 are formed by etching with the photoresist 420 as a mask, the ridge portion 201 generally has a shape feature of being narrow at the top and wide at the bottom. That is, the cross-section of the ridge portion 201 in the vertical direction is trapezoidal, and the angle between the bottom of the trapezoidal cross-section structure and the adjacent side is between 40° and 60°. The ridge-shaped part 201, which is narrow at the top and wide at the bottom, not only reduces the carrier injection efficiency and the output power of the laser, but also limits the lateral emission angle of the laser. This leads to an increase in the aspect ratio of the emitted laser from the semiconductor laser, making the emitted laser spot elliptical, which is not conducive to the application of the laser in subsequent products.

[0033] To avoid the aforementioned problems found in existing technologies, see [reference needed]. Figures 4-6This application involves pre-forming a hard mask layer 410 at a predetermined location on the epitaxial structure 200, including but not limited to growing silicon nitride (SiN) on the ridge portion 201. x ), with SiN x As a hard mask layer 410, replacing the photoresist 420 in the prior art, and using an inductively coupled plasma (ICP) etching machine to dry etch the epitaxial structure 200 to form the ridge 201 and the step region 202, this application obtains the ridge 201 with better sidewall verticality, improving the morphological characteristics of the narrow-bottom-wide trapezoidal cross-section structure of the ridge 201 in the prior art. In other words, this application utilizes SiN... x The hard mask layer 410 has superior verticality on its edge sidewalls. Therefore, during subsequent ICP dry etching, controlling the ridge portion 201 to have a rectangular or trapezoidal vertical cross-section, with the angle between the bottom of the cross-section and the adjacent sidewalls ranging from 70° to 90°, improves the verticality of the ridge portion 201 sidewalls, thereby improving the beam pattern of the emitted laser from the semiconductor laser and making the far-field beam more circular. The first barrier layer 310 is formed on the sidewalls of the step region and the ridge portion. Therefore, the angle between the first barrier layer 310 on the step region 202 and the sidewalls of the ridge portion 201 also ranges from 70° to 90°. Simultaneously, utilizing SiN... x The higher the verticality of the sidewall of the ridge 201 formed as a dry-etched hard mask layer, the smaller the width difference between its second end and the first end. This can further reduce the diffusion loss when charge carriers are injected into both sides of the ridge 201, increase the current injection density of charge carriers in the active region 230, improve the injection efficiency of charge carriers, and thus improve the output power of the laser.

[0034] Preferably, the width difference in the horizontal direction between the second end and the first end of the ridge portion 201 is between 0.1 μm and 0.3 μm.

[0035] It is important to note that during the process of forming the ridge 201 and the step region 202 using ICP dry etching, the etching reaction time and etching reaction rate of the epitaxial structure 200 must be strictly controlled in order to ensure that the step region 202 is formed on the second lower waveguide layer 241, and to avoid over-etching that could damage the active region 230.

[0036] Preferably, the thickness of the second waveguide layer 240 is controlled between 150 nm and 350 nm. Specifically, the thickness of the second upper waveguide layer 242 in the vertical direction is between 150 nm and 200 nm, and the thickness of the second lower waveguide layer 241 in the vertical direction is between 50 nm and 100 nm. Therefore, the etching depth for ICP dry etching to form the ridge portion 201 and the step region 202 needs to be controlled between 550 nm and 650 nm, that is, the thickness of the ridge portion 201 in the vertical direction is between 540 nm and 600 nm.

[0037] After the first barrier layer 310 is formed, the hard mask layer 410 located on the ridge portion 201 is removed by wet etching. The wet etching method for removing the hard mask layer 410 can effectively avoid the problem of damage or detachment of the insulating layer 320 on the sidewall of the ridge portion 201 caused by the removal of photoresist 420 in the prior art. That is, the wet etching removal of the hard mask layer 410 can avoid damage or detachment of the first barrier layer 310 covering the sidewall of the ridge portion 201, and avoid leakage caused by current diffusion to both sides of the ridge portion 201 or injection into the active region 230.

[0038] In one implementation, see Figure 1 The first confinement layer 210 and the first waveguide layer 220 are made of N-type semiconductor layers (e.g., semiconductor layers doped with elements such as Si, Ge, Sn, Se, and Te), while the second confinement layer 250 and the second waveguide layer 240 are made of P-type semiconductor layers (e.g., semiconductor layers doped with elements such as Mg, Zn, Ca, Sr, and Ba). The active region 230 is a multilayer quantum well. In one embodiment, the first confinement layer 210 is N-type doped aluminum gallium nitride (AlGaN) to confine the light field in the direction toward the substrate 100, and the second confinement layer 250 is P-type doped aluminum gallium nitride to confine the light field in the direction away from the substrate 100. The first waveguide layer 220 is N-type doped indium gallium nitride (InGaN), and the second waveguide layer 240 is P-type doped indium gallium nitride, which increases the confinement of charge carriers, increases the distribution of charge carriers in the active region 230, improves the light confinement factor, reduces the threshold current, and improves the luminous efficiency. The active region 230 is a multi-layer indium gallium nitride / gallium nitride (GaN) quantum well, grown in alternating periods, to provide optical gain. In another embodiment, the active region 230 may also be a single quantum well layer composed of indium gallium nitride / gallium nitride (GaN).

[0039] The first barrier layer 310 is configured as an N-type semiconductor layer with the same conductivity type as the first confinement layer 210 and / or the first waveguide layer 220. This allows a space charge region to be formed between the first barrier layer 310 and the second waveguide layer 240. A strong built-in electric field exists within this space charge region, hindering the expansion of majority carriers on both sides of the ridge 201 towards the sides of the ridge 201. In other words, during current injection, the first barrier layer 310 can suppress the expansion of hole carriers towards the sides of the ridge 201, thereby improving carrier injection efficiency. The first barrier layer 310 comprises N-type gallium nitride material.

[0040] Specifically, metal-organic chemical vapor deposition (MOCVD) can be used to generate N-type doped aluminum gallium nitride at high temperature on the sidewalls of the step region 202 and the ridge portion 201. The generated N-type aluminum gallium nitride is used as the first barrier layer 310, which is combined with the P-type doped second confinement layer 250 and the second waveguide layer 240, as well as the N-type doped first confinement layer 210 and the first waveguide layer 220 to form an NPN junction when the laser is forward-biased. This blocks the lateral expansion of hole carriers to both sides of the ridge portion 201, avoids leakage current on both sides of the ridge portion 201, improves the injection efficiency of hole carriers into the active region 230, and thus improves the output power of the laser.

[0041] Preferably, the thickness of the first barrier layer 310 is between 200 nm and 700 nm. Specifically, the thickness of the first barrier layer 310 in the vertical direction on the step region 202 is between 500 nm and 700 nm. Since the deposition of the first barrier layer 310 on the sidewalls of the ridge portion 201 is more difficult than on the step region 202, the thickness of the first barrier layer 310 in the horizontal direction on the sidewalls of the ridge portion is between 150 nm and 450 nm, which is less than the thickness of the first barrier layer 310 in the vertical direction on the step region 202. Furthermore, the MOCVD process used in this embodiment is more conducive to the deposition of the first barrier layer 310 on the sidewalls of the ridge portion 201 and improves the film quality of the first barrier layer 310.

[0042] It should be understood that the specific methods for generating the first barrier layer 310 and the materials used described above are merely illustrative examples and should not be construed as limiting the methods for generating the first barrier layer 310 or the materials used. In other words, the first barrier layer 310 can also be an N-type doped semiconductor layer generated by other methods.

[0043] In one implementation, participants Figure 1The epitaxial structure 200 further includes a second blocking layer 260, which is disposed between the second waveguide layer 240 and the second confinement layer 250. This blocking layer 260 is used to prevent electrons in the active region 230 from overflowing from the second confinement layer 250 when the semiconductor laser is forward-biased, thereby affecting the output power of the semiconductor laser. In this application, the ridge portion 201 is configured to extend upward from the second waveguide layer 240, including at least a second upper waveguide layer 242 and a second confinement layer 250. That is, the second blocking layer 260 is also located within the ridge portion 201 and is disposed between the second upper waveguide layer 242 and the second confinement layer 250. Its vertical projection on the substrate 100 lies within the vertical projection plane of the ridge portion 201 on the substrate 100, thus preventing electrons in the active region 230 from overflowing towards the first end of the ridge portion 201.

[0044] Preferably, the second barrier layer 260 is configured as a P-type semiconductor layer with the same conductivity type as the second confinement layer 250 and / or the second waveguide layer 240, including but not limited to using P-type doped aluminum gallium nitride, to form a barrier between the second waveguide layer 240 and the second confinement layer 250 to prevent electrons from overflowing from the active region 230.

[0045] In one implementation, see Figure 7 The substrate 100 includes, but is not limited to, a silicon carbide substrate, a silicon substrate, or a gallium nitride substrate, with the substrate 100 preferably being a gallium nitride substrate. A buffer layer 500 is formed on the substrate 100, and the epitaxial structure 200 described above is formed on the surface of the buffer layer 500 away from the substrate 100. Distributing the buffer layer 500 between the epitaxial structure 200 and the substrate 100 can effectively alleviate the stress generated between the epitaxial structure 200 and the substrate 100 due to lattice mismatch during epitaxial growth, which is beneficial for reducing the defect rate of the epitaxial structure 200 during epitaxial growth.

[0046] Furthermore, participate Figure 8 A first electrode layer 620 is provided on the bottom surface of the substrate 100 on the side away from the epitaxial structure 200. A stacked ohmic contact layer 610 and a second electrode layer 630 are provided on the ridge portion 201. The first electrode layer 620 and the second electrode layer 630 are typically made of metal as electrodes to electrically connect with the outside world to control the conduction of the semiconductor laser. The ohmic contact layer 610 covers the first end of the ridge portion 201 (the upper surface of the second confinement layer 250) and the cross-section of the first barrier layer 310 on both sides of the ridge portion 201. The second electrode layer 630 is located on the ohmic contact layer 610, which can prevent the second electrode layer 630 from forming a Schottky contact directly with the second confinement layer 250, thereby reducing the contact resistance and improving the current transmission efficiency and operational stability of the semiconductor laser.

[0047] In another implementation, see Figure 9 The ohmic contact layer 610 is formed only on the ridge portion, and the first barrier layer 310 not only covers the sidewall of the ridge portion 201, but also extends upward to cover the sidewall and upper surface of the ohmic contact layer 610, and leaves an opening on the ridge portion 201 to expose part of the upper surface of the ohmic contact layer 610 so that the second electrode layer 630 can maintain an electrical connection with the ohmic contact layer 610 through the opening.

[0048] Preferably, the ohmic contact layer 610 may be composed of a p-type doped semiconductor material, including but not limited to p-type doped gallium nitride. The ohmic contact layer 610 may also be composed of a transparent conductive material, including but not limited to indium tin oxide.

[0049] This application provides a semiconductor laser, including a substrate 100, on which an epitaxial structure 200 is formed. A first barrier layer 310 is formed on the epitaxial structure 200, which further includes, from bottom to top, a first confinement layer 210, a first waveguide layer 220, an active region 230, a second waveguide layer 240, and a second confinement layer 250. The second confinement layer 250 and a portion of the second waveguide layer 240 are configured as protrusions extending vertically away from the substrate 100 to form a ridge 201, and stepped regions 202 are formed on the second waveguide layers 240 on both sides of the ridge 201. By placing the bottom end of the ridge 201 on the second waveguide layer 240 near the active region 230, the injection area for carriers into the active region 230 is reduced when the semiconductor laser is forward-biased, thereby improving carrier injection efficiency and increasing the output power of the semiconductor laser.

[0050] Meanwhile, by setting the second barrier layer 260 on the sidewalls of the step region 202 and the ridge portion 201, and setting the conductivity type of the first barrier layer 310 to be the same as that of the first confinement layer 210 and the first waveguide layer 220, and different from that of the second waveguide layer 240 and the second confinement layer 250, an NPN junction is formed. This can replace the insulating layer 320 in the prior art, effectively preventing leakage caused by the diffusion of some charge carriers to both sides of the ridge portion 201, or injecting the active region 230 from both sides of the ridge portion 201, and further improving the carrier injection efficiency, thereby achieving the purpose of increasing the output power of the semiconductor laser.

[0051] Furthermore, this application forms a hard mask layer 410 at a predetermined position in the epitaxial structure 200 and uses a combined IPC dry etching process to obtain a ridge portion 201 with better sidewall verticality. This improves the top-narrow and bottom-wide topographic features of the ridge portion 201 formed by photolithography in the prior art, avoids the problem of elliptical laser spot caused by the large aspect ratio of the emitted laser in the existing semiconductor laser, and improves the light output effect of the semiconductor laser.

[0052] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of this application, and these improvements and substitutions should also be considered within the scope of protection of this application.

Claims

1. A semiconductor laser, characterized in that, include: Substrate; An epitaxial structure is formed on the substrate, including a ridge portion and a stepped region, wherein the angle between the bottom of the ridge portion and the adjacent side in the vertical cross section is between 70° and 90°. A first barrier layer is formed on the extensional structure, the first barrier layer covering the stepped area and extending to cover the sidewall of the ridge portion; The epitaxial structure includes a first confinement layer, a first waveguide layer, an active region, a second waveguide layer, and a second confinement layer stacked from bottom to top. The ridge portion is configured as a protrusion extending upward from inside the second waveguide layer in a direction away from the substrate, and includes at least the second confinement layer and a portion of the second waveguide layer. The step region is formed on the second waveguide layers on both sides of the ridge portion. The second waveguide layer includes a second upper waveguide layer and a second lower waveguide layer, and the stepped region is formed on the second lower waveguide layer on both sides of the second upper waveguide layer; the thickness of the second lower waveguide layer in the vertical direction is between 50nm and 100nm. The ridge portion has a stacked ohmic contact layer and a second electrode layer; the first barrier layer covers the sidewall of the ridge portion, extends upward to cover the sidewall and upper surface of the ohmic contact layer, and has an opening on the ridge portion that exposes a portion of the upper surface of the ohmic contact layer.

2. The semiconductor laser according to claim 1, characterized in that, The first barrier layer has the same conductivity type as the first confinement layer and the first waveguide layer, but a different conductivity type from the second waveguide layer and the second confinement layer; the first barrier layer is formed by a deposition process.

3. The semiconductor laser according to claim 1, characterized in that, The first barrier layer contains gallium nitride material.

4. The semiconductor laser according to claim 1, characterized in that, The thickness of the first barrier layer ranges from 200nm to 700nm.

5. The semiconductor laser according to claim 4, characterized in that, The thickness of the first barrier layer in the vertical direction of the stepped area is between 500 nm and 700 nm, and the thickness in the horizontal direction of the sidewall of the ridge portion is between 150 nm and 450 nm.

6. The semiconductor laser according to claim 1, characterized in that, The angle between the first barrier layer on the stepped area and the sidewall of the ridge portion is between 70° and 90°.

7. The semiconductor laser according to claim 1, characterized in that, The ridge extends upward from the second upper waveguide layer and includes the second upper waveguide layer and the second confinement layer.

8. The semiconductor laser according to claim 1, characterized in that, The thickness of the second upper waveguide layer in the vertical direction is between 150nm and 200nm.

9. The semiconductor laser according to claim 1, characterized in that, The thickness of the ridge portion in the vertical direction ranges from 550 nm to 650 nm.

10. The semiconductor laser according to claim 1, characterized in that, The ridge portion has a rectangular or trapezoidal cross-section in the vertical direction.

11. The semiconductor laser according to any one of claims 1 or 10, characterized in that, The width difference between the bottom and top of the ridge portion in the vertical cross-section ranges from 0.1 μm to 0.3 μm.

12. The semiconductor laser according to claim 1, characterized in that, The substrate has a first electrode layer at its bottom.

13. The semiconductor laser according to claim 1, characterized in that, The epitaxial structure further includes a second blocking layer, which is located between the second confinement layer and the second waveguide layer.

14. The semiconductor laser according to claim 13, characterized in that, The second barrier layer has the same conductivity type as the second waveguide layer.

15. The semiconductor laser according to claim 13, characterized in that, The vertical projection of the second barrier layer on the substrate lies within the vertical projection plane of the ridge portion on the substrate.

16. The semiconductor laser according to claim 1, characterized in that, The first confinement layer comprises N-type doped aluminum gallium nitride, the first waveguide layer comprises N-type doped indium gallium nitride, the second confinement layer comprises P-type doped aluminum gallium nitride, and the second waveguide layer comprises P-type doped indium gallium nitride.

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